Piezoelectric thin film, piezoelectric thin film element, and piezoelectric transducer

Abstract

A piezoelectric thin film contains a metal oxide having a perovskite structure. The metal oxide contains bismuth, potassium, titanium, magnesium, iron, and an element M. The element M is at least one element selected from the group consisting of gallium and cobalt. At least a part of the metal oxide is at least one crystal selected from the group consisting of a tetragonal crystal and an orthorhombic crystal. A (001) plane of the crystal is oriented in a normal direction of a surface of the piezoelectric thin film.

What is claimed is: 
     
         1 . A piezoelectric thin film comprising a metal oxide having a perovskite structure, wherein
 the metal oxide contains bismuth, potassium, titanium, magnesium, iron, and an element M,   the element M is at least one element selected from the group consisting of gallium and cobalt,   at least a part of the metal oxide is at least one crystal selected from the group consisting of a tetragonal crystal and an orthorhombic crystal, and   a (001) plane of the crystal is oriented in a normal direction of a surface of the piezoelectric thin film.   
     
     
         2 . The piezoelectric thin film according to  claim 1 , wherein the metal oxide is represented by Chemical Formula 1 below,
 each of x, y, and z in Chemical Formula 1 below is a positive real number,   x+y+z is 1,   α in Chemical Formula 1 below is more than 0 and less than 1,   β in Chemical Formula 1 below is more than 0 and less than 1,   γ in Chemical Formula 1 below is from 0.05 to 0.40,   M in Chemical Formula 1 below is represented by Ga 1−δ Co δ , and   δ is from 0 to 1,
     x (B 1−α K α )TiO 3 - y Bi(Ti 1−β Mg β )O 3 - z Bi(Fe 1−γ M γ )O 3   (1)
 
   
     
     
         3 . The piezoelectric thin film according to  claim 2 , wherein a three-dimensional coordinate system is composed of an X-axis, a Y-axis, and a Z-axis,
 arbitrary coordinates in the coordinate system are represented by (X, Y, Z),   coordinates (x, y, z) in the coordinate system correspond to x, y, and z in Chemical Formula 1 above,   coordinates A in the coordinate system are (0.250, 0.005, 0.700),   coordinates B in the coordinate system are (0.450, 0.250, 0.300),   coordinates C in the coordinate system are (0.200, 0.500, 0.300),   coordinates D in the coordinate system are (0.005, 0.250, 0.700), and   the coordinates (x, y, z) are positioned within a quadrangle with vertexes at the coordinates A, the coordinates B, the coordinates C, and the coordinates D.   
     
     
         4 . The piezoelectric thin film according to  claim 1 , wherein the piezoelectric thin film is an epitaxial film. 
     
     
         5 . The piezoelectric thin film according to  claim 1 , wherein the piezoelectric thin film is a ferroelectric thin film. 
     
     
         6 . A piezoelectric thin film element comprising the piezoelectric thin film according to  claim 1 . 
     
     
         7 . The piezoelectric thin film element according to  claim 6 , comprising:
 a crystalline substrate; and   the piezoelectric thin film directly or indirectly stacked on the crystalline substrate.   
     
     
         8 . The piezoelectric thin film element according to  claim 6 , comprising:
 a crystalline substrate;   an electrode layer directly or indirectly stacked on the crystalline substrate; and   the piezoelectric thin film directly or indirectly stacked on the electrode layer.   
     
     
         9 . The piezoelectric thin film element according to  claim 6 , comprising:
 an electrode layer; and   the piezoelectric thin film directly or indirectly stacked on the electrode layer.   
     
     
         10 . The piezoelectric thin film element according to  claim 8 , further comprising at least one intermediate layer, wherein
 the intermediate layer is disposed between the crystalline substrate and the electrode layer.   
     
     
         11 . The piezoelectric thin film element according to  claim 8 , further comprising at least one intermediate layer, wherein
 the intermediate layer is disposed between the electrode layer and the piezoelectric thin film.   
     
     
         12 . The piezoelectric thin film element according to  claim 9 , further comprising at least one intermediate layer, wherein
 the intermediate layer is disposed between the electrode layer and the piezoelectric thin film.   
     
     
         13 . The piezoelectric thin film element according to  claim 8 , wherein the electrode layer contains a platinum crystal,
 a (002) plane of the platinum crystal is oriented in a normal direction of a surface of the electrode layer, and   a (200) plane of the platinum crystal is oriented in an in-plane direction of the surface of the electrode layer.   
     
     
         14 . The piezoelectric thin film element according to  claim 9 , wherein the electrode layer contains a platinum crystal,
 a (002) plane of the platinum crystal is oriented in a normal direction of a surface of the electrode layer, and   a (200) plane of the platinum crystal is oriented in an in-plane direction of the surface of the electrode layer.   
     
     
         15 . A piezoelectric transducer comprising the piezoelectric thin film according to  claim 1 . 
     
     
         16 . A piezoelectric transducer comprising the piezoelectric thin film element according to  claim 6 .